I've been trying to figure out why I didn't enjoy my 3D World
viewer as much as I felt I should. My eyes frequently seemed
distracted rather than settled on the image. I diddled with my
focusing viewer this weekend and have put a page of notes at:
http://stereo.thurstons.us/content/?page_id=135

For immediate (and archive) reference, here are the important bits:

The 3D World focusing viewer includes two baffles restricting the
view. By design, these baffles were out of the path of the
image. They did not vignette or clip any part of the image. They
were, however, visible and I suspected they were distracting my
eye and drawing my attention away from the image.

The apertures behind the lens cones are rectangular and easily
visible. To test my hypothesis, all I had to do is open these
apertures a bit and reinstall the lens cones.

Removing the lens cones from the carrier was actually more
difficult than wielding the dremel tool used to enlarge the openings.

When I dropped a slide in the modified viewer, I noticed a couple
of things. Removing the close-in mask did reduce
eye-distraction. My eyes spent more time on the image and less
time darting in to check on this “thing” close to my eyeball.
This was good, but in fixing one deficiency, I had created another.

In my newly modified viewer, both images were easily visible to
both eyes.

With a little bit of styrene and a sharp pair of scissors, I
created an extension for the viewer’s short septum. It was
easily shaped to clear the nose indentation and the focusing rod,
and a dab of glue held it in place.

The results of all this are an increase in my satisfaction with
the viewer. With the apertures gone, my eyes spend less time
checking that little bit of close-in visual noise. Yes, it’s a
small improvement, but it is a small improvement I will make to
my other 3D World focusing viewer the next time I have it apart.
I’d suggest that a taller septum and larger lens apertures
would be low cost improvements the manufacturer could incorporate
in the future.

As always, on-topic comments are welcome. If there are editorial
difficulties with my content or technical problems with content
delivery, please contact me _off list_. We don't need to bore
everyone with news of my poor spelling or web server malfunctions.

John Thurston
Juneau, Alaska